Links between Gulf rivers and coastal productivity wrap-up

14 December 2021

The Mitchell, Gilbert and Flinders rivers flow into the south-eastern Gulf of Carpentaria, supporting healthy ecosystems and nationally significant wetlands as well as important recreational and commercial fisheries. Banana prawns, barramundi and other important fishery species use estuarine ecosystems at different points throughout their life cycles. The Queensland Government has also identified these river systems as catchments where irrigated agriculture is already occurring or likely to occur.

 

Mitchell River drone image, looking down on mangroves and floodplains to the right and river winding away to the left with a research boat as a small dot in the distance.

Research was conducted in Gulf estuaries through fieldwork and remote sensing. Photo Stephen Faggotter.

This project has provided important new information about why freshwater flows in the Gulf estuaries and floodplains are essential for banana prawn and barramundi fisheries and the broader estuarine ecosystem, and modelled the potential scale of the impact of water extraction on the fisheries. This information ensures that water managers and planners know which flow characteristics of the rivers are most important for the region’s plants and animals so they can make fully informed decisions about any possible trade-offs.

This project increased the available knowledge about the nutrient concentrations from wet-season flows, the productivity in the three river estuaries and floodplains, how changes in flows might affect Gulf fishery catches and the possible economic impacts of future changes.

 

Gulf rivers map

Location of the three study rivers in north Queensland.

The project reinforced the understanding that flows in these three rivers are highly variable – both interannually and between rivers in any given year. Maintaining flows in low- and medium-flow years is critical for sustaining estuarine productivity. This has flow-on effects to the whole food web that relies on primary producers such as algae. This research has helped quantify the major impacts that water extraction in years following multiple years of low-to-medium flow would have, and the possible climate and weather changes that could amplify these effects.

The researchers suggest that, given the natural variability of the Gulf systems, it will take years to determine the impacts of water development on productivity in the estuaries, so any water allocation should occur on a precautionary basis. The modelling capacity developed in this project has the potential to be used by management agencies to evaluate future water-resource development scenarios and provide a platform which can be enhanced over time as new knowledge is developed.

To find out more about the broader findings for future water planning, estuarine productivity, floodplain productivity and implications for banana prawn and barramundi fisheries, head to the executive summary for an overview or the respective reports.

 

Prawn trawler moored at a jetty in Karumba with a billowing wet season cloud in the background.

Prawn trawler moored at a jetty in Karumba with a billowing wet season cloud in the background. Photo: Michele Burford.

 

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